1891 Mar 3. Born Down
1921 Apr 1. RIC no 80836 & ADRIC 508
Posted to D Coy
The only census entry of right age is living at Ballyalton, Newtownards South, Down

It does not seem to be
1911 census Private John Boyd age 18 is a Private in 5th Lancers stationed at Woolwich. Born Newry , Down